Flat lamp

ABSTRACT

A flat lamp is provided, including an upper plate and a lower plate arranged to face each other at a predetermined distance; a plurality of spacers installed between the upper plate and the lower plate to form discharge spaces; a first and second electrodes provided in a stripe form on the outer surface of the upper plate or the lower plate with the respective discharge spaces located thereon; a first and second inner electrodes provided within each of the spacers; and a fluorescent layer formed on each of inner surfaces of the upper and lower plates and each of the outer surfaces of the spacers.

BACKGROUND OF THE INVENTION

This application claims the priority of Korean Patent Application No.2003-72138, filed on Oct. 16, 2003, in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein in its entiretyby reference.

1. Field of the Invention

The present invention relates to a flat lamp, and more particularly, toa flat lamp having a high brightness, a high luminous efficiency, and auniform distribution of brightness.

2. Description of the Related Art

Flat lamps mainly used as back-light of liquid crystal displays (LCDs)have been developed into surface discharge type or facing surfacesdischarge type lamps, in which the entire space under a light emittingsurface makes a discharge space considering the luminous efficiency anduniformity of brightness, from conventional edge-light or direct-lighttype lamps using a cold cathode fluorescent lamp.

In general, the surface discharge type is advantageous in that adischarge characteristics is stable compared to the facing surfacesdischarge type. However, the overall brightness of the surface dischargetype is lower than that of the facing surfaces discharge type. As anexample of a conventional surface discharge flat lamp, there is a lampin which the overall discharge space is divided into fine dischargeareas to prevent local concentration of discharge. This lamp candischarge stably. However, since the uniformity of the overallbrightness is inferior due to a difference in the brightness and a gapbetween the fine discharge areas, a diffusing paper or diffusing plateis needed to uniformly diffuse light.

FIG. 1 shows another example of a conventional surface discharge typeflat lamp. Referring to FIG. 1, discharge spaces filled with dischargegas are formed between an upper plate 20 and a lower plate 10 separatedat a predetermined distance by a plurality of spacers 14.

A fluorescent layer 30 is formed on each of the inner surfaces of theupper and lower plates 20 and 10 and at both sides of the spacers 14.Pairs of electrodes including a first and second upper electrodes 22 aand 22 b and a first and second lower electrodes 12 a and 12 b areprovided, respectively, on the outer surfaces of the upper and lowerplates 20 and 10, which correspond to the respective discharge spaces.The first upper electrode 22 a and the first lower electrode 12 a facingeach other maintain the same electric potential so that discharge is notinduced therebetween. Also, the second upper electrode 22 b and thesecond lower electrode 12 b facing each other maintain the same electricpotential so that discharge is not induced therebetween. Meanwhile, apredetermined electric potential difference is present between the upperelectrode pair 22 a and 22 b and the lower electrode pair 12 a and 12 bso that discharge is induced between the electrode pairs in a directionparallel to the upper plate 20 or the lower plate 10.

In the flat lamps having the above structure, it is disadvantageous thatsince the first and second upper electrodes 22 a and 22 b on the upperplate 20 and the spacers 14 interfere light generated by a discharge, itis difficult to obtain uniform light. Also, when partial pressure of thedischarge gas is increased, the discharge voltage highly increases.

SUMMARY OF THE INVENTION

The present invention provides a flat lamp having a high brightness, ahigh luminous efficiency, and a uniform distribution of brightness byhaving electrodes within spacers.

According to an aspect of the present invention, there is provided aflat lamp including an upper plate and a lower plate arranged to faceeach other at a predetermined distance; a plurality of spacers installedbetween the upper plate and the lower plate to form discharge spaces; afirst and second electrodes provided in a stripe form on the outersurface of the upper plate or the lower plate with the respectivedischarge spaces located thereon; a first and second inner electrodesprovided within each of the spacers; and a fluorescent layer formed oneach of inner surfaces of the upper and lower plates and each of outersurfaces of the spacers.

The spacers may be arranged in a direction parallel to the first andsecond electrodes and the first and second inner electrodes are providedalong both lateral sides within the spacers.

The spacers may be in the form of a cylinder or circular pipe. When thespacers are in the form of a circular pipe, the fluorescent layer mayalso be formed on each of inner surfaces of the spacers.

The spacers may be formed of glass.

According to another aspect of the present invention, there is provideda flat lamp including an upper plate; a lower plate arranged to face theupper plate and having a plurality of flat portions separated by apredetermined distance from the upper plate and a plurality ofprotrusion portions projecting between the flat portions, of which topsurfaces contact the inner surface of the upper plate to form dischargespaces; a first and second electrodes provided in a stripe form on theouter surface of the upper plate or the lower plate with the respectivedischarge spaces located thereon; a first and second inner electrodesprovided within each of the protrusion portions; and a fluorescent layerformed on each of inner surfaces of the upper and lower plates.

The protrusion portions may be arranged in a direction parallel to thefirst and second electrodes, and the first and second inner electrodesmay be provided along both lateral sides within the protrusion portions.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a perspective view schematically showing a conventional flatlamp;

FIG. 2 is a perspective view schematically showing a flat lamp accordingto an embodiment of the present invention;

FIG. 3 is a cross-sectional view of the flat lamp of FIG. 2;

FIGS. 4A and 4B are diagrams showing discharge voltage and intensity oflight during discharge of the conventional flat lamp and those of theflat lamp according to the present invention, respectively;

FIGS. 5A and 5B are photographs of upper plates during discharge of theconventional flat lamp and the flat lamp according to the presentinvention, respectively;

FIGS. 6A through 6C are diagrams showing the flat lamp according to thepresent invention when voltage is applied only to a first and secondelectrodes, when voltage is applied only to a first and second innerelectrodes, and when voltage is applied to both the first and secondelectrodes and the first and second inner electrodes, respectively; and

FIG. 7 is a perspective view schematically showing a flat lamp accordingto another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described more fully with reference tothe accompanying drawings, in which embodiments of the invention areshown. In the drawings, like reference numbers refer to like elementsthroughout.

FIGS. 2 and 3 are a perspective view and a vertical cross-sectional viewof a flat lamp according to the present invention, respectively.

Referring to FIGS. 2 and 3, an upper plate 120 and a lower plate 110 arearranged to face each other at a predetermined distance. The upper plate120 and the lower plate 110 may be formed of glass. A plurality ofspacers 114 are provided between the upper plate 120 and the lower plate110, so that the upper plate 120 and the lower plate 110 are separatedby a predetermined distance. The spacers 114 are separated by apredetermined distance in parallel to each other, and are in the form ofa circular pipe. The spacers 114 are formed of glass. Meanwhile, thespacers 114 may be in the form of a cylinder. By the spacers 114, aplurality of discharge spaces are formed between the upper plate 120 andthe lower plate 110. The discharge spaces are filled with discharge gasto generate ultraviolet rays during discharge.

A first and second electrodes 112 a and 112 b are provided on the outersurface of the lower plate 110 with the respective discharge spaceslocated thereon, in a direction parallel to the spacers 114 and in astripe form. Alternatively, the first and second electrodes 112 a and112 b may be provided on the outer surface of the upper plate 120.

A first and second inner electrodes 150 a and 150 b are provided withinthe spacers 114. The first and second inner electrodes 150 a and 150 bare provided along both lateral sides within the spacer 114. The firstand second inner electrodes 150 a and 150 b are formed of a conductivematerial.

A fluorescent layer 130 is formed on each of the inner surfaces of theupper and lower plates 120 and 110 and each of outer surfaces of thespacers 114. Alternatively, the fluorescent layer 130 may also be formedon the inner surface of the spacer 114 in the form of a circular pipe. Areflection layer may be interposed between the fluorescent layer 130 andthe lower plate 110, so that entire light generated in the dischargespaces proceeds toward the upper plate 120.

In the flat lamp having the above structure, when voltage is applied tothe first and second electrodes 112 a and 112 b and the first and secondinner electrodes 150 a and 150 b, respectively, as shown in FIG. 3,discharge is induced within the discharge spaces. Here, the discharge isinduced by an electric field which is formed by the first and secondelectrodes 112 a and 112 b on the outer surface of the lower plate 110and an electric field which is formed by the first and second innerelectrodes 150 a and 150 b within each of the adjacent spacers 114. Thefirst and second inner electrodes 150 a and 150 b provided within of thespacer 114 are arranged to face to those of an adjacent spacer 114,thereby inducing a facing type electric field. Thus, the discharge isactively induced even at low voltage.

Meanwhile, the upper plate having the inner surface contacting thespacers 114 in the form of a circular pipe has a reduced contact area.Thus, light proceeds toward the upper plate 120 without interference ofspacers 114, resulting in an improved uniformity of light. In addition,the area of the outer surface of the spacer 114 coated with thefluorescent layer 130 is increased, resulting in more light.

FIGS. 4A and 4B show the discharge voltage and the intensity of lightduring discharge of the conventional flat lamp compared to the flat lampaccording to an embodiment of the present invention. FIGS. 4A and 4Bshow the test results measured using the discharge space filled with 10%Ne—Xe discharge gas at the discharge gas pressure of 260 mbar.

First, referring to FIG. 4A, the conventional flat lamp has a dischargestarting voltage V_(f) and a discharge maintenance voltage V_(s) of 2.68kV and 1.7 kV, respectively. When entire light generated throughdischarge by applying the voltage of 2 kV proceeds toward the upperplate 20, the intensity of light is 1549 cd/m². Next, referring to FIG.4B, the flat lamp according to the present invention has the dischargestarting voltage V_(f) and the discharge maintenance voltage V_(s) of1.98 kV and 1.33 kV, respectively. When entire light generated throughdischarge by applying of the voltage of 2 kV proceeds toward the upperplate 120, the intensity of light is 1633 cd/m².

Comparing such results, the discharge starting voltage and the dischargemaintenance voltage of the flat lamp according to the present inventionare lower than those of the conventional flat lamp. The intensity oflight proceeding toward the upper plate 120 of the flat lamp accordingto the present invention is higher than that of the conventional flatlamp. Thus, when using the flat lamp of the present invention, theluminous efficiency and brightness can be improved.

FIGS. 5A and 5B are photographs of the upper plates during discharge ofthe conventional flat lamp and the flat lamp according to an embodimentof the present invention.

In the conventional flat lamp, since light emitted toward the upperplate (20 in FIG. 4A) is interrupted by the spacer 14, the first andsecond upper electrodes 22 a and 22 b, a spacer pattern 70 and anelectrode pattern 60, as shown in FIG. 5A, are formed. On the contrary,since the flat lamp of the present invention has the first and secondinner electrodes 150 a and 150 b provided within the spacers (114 inFIG. 4B) in the form of a circular pipe, neither the spacer pattern (70in FIG. 5A) nor the electrode pattern (60 in FIG. 5A) are shown.Accordingly, when using the flat lamp of the present invention, theuniformity of light can be improved.

FIGS. 6A through 6C show the flat lamps according to an embodiment ofthe present invention in the cases of applying the voltage only to thefirst and second electrodes 112 a and 112 b, only to the first andsecond inner electrodes 150 a and 150 b, and to both the first andsecond electrodes 112 a and 112 b and the first and second innerelectrodes 150 a and 150 b. When applying the voltage as describedabove, the discharge starting voltage is highest in the case of applyingthe voltage only to the first and second electrodes 112 a and 112 b, asshown in FIG. 6A, and is lowest in the case of applying the voltage toboth the first and second electrodes 112 a and 112 b and the first andsecond inner electrodes 150 a and 150 b, as shown in FIG. 6C.

FIG. 7 is a perspective view of the flat lamp according to anotherembodiment of the present invention.

Referring to FIG. 7, the flat lamp has an upper plate 220 and a lowerplate 210 arranged to face to each other. The upper plate 220 and thelower plate 210 may be formed of glass. The lower plate 210 has aplurality of flat portions 210 a separated by a predetermined distancefrom the upper plate 220 and a plurality of protrusion portions 210 bprojecting between the flat portions 210 a. The protrusion portions 210b function as the spacers in the flat lamp according to an embodiment ofthe present invention. That is, the top surfaces of the protrusionportions 210 b contact the inner surface of the upper plate 220, suchthat the flat portions 210 a are separated by a predetermined distancefrom the upper plate 220. The protrusion portions 210 b spacing at apredetermined distance are arranged in a direction parallel to eachother. Such protrusion portions 210 b form a plurality of dischargespaces between the upper plate 220 and the lower plate 210. Thedischarge spaces are filled with discharge gas to generate ultravioletrays during discharge.

A first and second electrodes 212 a and 212 b are provided on the outersurface of the flat portions 210 a of the lower plate 210 with therespective discharge spaces located thereon, in a direction parallel tothe protrusion portions 210 b and in a stripe form. Alternatively, thefirst and second electrodes 212 a and 212 b may be provided on the outersurface of the upper plate 220 with the respective discharge spaceslocated thereon.

The protrusion portions 210 b have a first and second inner electrodes250 a and 250 b provided therein. The first and second inner electrodes250 a and 250 b are arranged along both lateral sides within theprotrusion portion 210 b.

A fluorescent layer is formed on each of the inner surfaces of the upperplate 220 and the lower plate 210. Meanwhile, a reflection layer (notshown) is interposed between the fluorescent layer 230 and the lowerplate 210, so that entire light generated at the discharge space duringdischarge proceeds toward the upper plate 220.

In the flat lamp having the above structure, when applying the voltageto each of the first and second electrodes 212 a and 212 b and the firstand second inner electrodes 250 a and 250 b, discharge is generatedwithin the discharge space. Here, the discharge is generated by anelectric field which is formed by the first and second electrodes 212 aand 212 b on the flat portion 210 a of the lower plate 210 and anelectric field which is formed by the first and second inner electrodes250 a, 250 b within the adjacent protrusion portions 210 b. The firstand second inner electrodes 250 a and 250 b provided in the innerlateral side of the protrusion portion 210 b face to those of anadjacent protrusion 210 b, so that a facing type electric field isinduced. Thus, discharge can actively be induced even at low voltage.

As described above, a flat lamp according to the present invention hasthe following effects.

First, the electrodes are provided within the spacers to induce a facingtype electric field, thereby actively inducing discharge even at lowvoltage.

Second, the spacers in the form of a cylinder or circular pipe areprovided between the upper plate and the lower plate, so that lightproceeds toward the upper plate without interference of the spacers,thereby improving the uniformity of light.

Third, the area coated with a fluorescent material is increased togenerate more light, thereby improving brightness.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1-6. (canceled)
 7. A flat lamp comprising: an upper plate; a lower platearranged to face the upper plate and having a plurality of flat portionsseparated by a predetermined distance from the upper plate and aplurality of protrusion portions projecting between the flat portions,of which top surfaces contact the inner surface of the upper plate toform discharge spaces; first and second electrodes provided in a stripeform on an outer surface of the upper plate or the lower plate with therespective discharge spaces located thereon; first and second innerelectrodes provided within each of the protrusion portions; and afluorescent layer formed on each of inner surfaces of the upper andlower plates.
 8. The flat lamp of claim 7, wherein the protrusionportions are arranged in a direction parallel to the first and secondelectrodes.
 9. The flat lamp of claim 7, wherein the first and secondinner electrodes are provided along both lateral sides of the protrusionportions.